normplot(X)

Produce a normal probability plot for each column of X.
The line joing the 1st and 3rd quantile is drawn on the
graph.  If the underlying distribution is normal, the
points will cluster around this line.

Note that this function sets the title, xlabel, ylabel,
axis, grid, tics and hold properties of the graph.  These
need to be cleared before subsequent graphs using 'clf'.